This invention relates to laminated materials for the production of plain bearing elements which are capable of withstanding great pressures and high temperature, which are wear resistant and which need no maintenance. The invention also relates to methods for the production of such laminated plain bearing materials.
A number of bearing materials based on natural and synthetic substances are already known, which have a low coefficient of friction in the dry state and at the same time are permanently heat-resistant to temperatures of 100.degree. C. and more, such materials being the fluorine-containing polymers and graphite. The use of these materials in textile form for slide surface linings or facings is also known; but their usage encounters the difficulty that an adequate bond cannot be obtained with the backing or supporting body through the known cementing or vulcanizing procedures.
It has already been attempted to overcome this difficulty by interweaving, in a known weaving process, threads made of a low-friction material with threads made of a material that is readily joinable by cementing or vulcanizing, in such a manner that the low-friction threads are located on one side of the fabric or facing and the readily-joinable threads located on the other. Such a fabric is then intended to be cemented or vulcanized with its side having the readily-joinable threads to a prepared backing or bearing support strip or body (German Pat. No. 1,174,122). However, it has so far not been possible to produce in this manner a laminated plain bearing material which can be conventionally processed into plain bearing elements in a manufacturing operation used for plain bearings, because the bonding strength attained to date is manifestly insufficient to process (bend, shape etc.) such a laminated material into the required plain bearings. And any individualized application of a bearing surface or facing to a prepared foundation base (supporting) body leads to an expensive production method which is feasible only for small-lot production and clearly not economical for practical requirements, despite the known increase in compressive strength which results from the inclusion of a fabric structure in the bearing material (U.S. Pat. No. 2,322,771).
As practical experience teaches, a better bond cannot be achieved either by using a fabric thread material (U.S. Pat. No. 3,037,893) in which the strands or thread materials are composed of carbon-fluoride resin fibers with at least one other type of fiber of a material having better bonding capability to the base or bearing support material than the carbon-fluoride resin. Even using such low friction fabrics, a working bond can only be established with prepared surfaces of the bases or bearing support bodies.
A multiplicity of different attempts to build up the bearing surface of a plain bearing element with fiber material or fabric has also been undertaken. It is known, for example, to use inorganic fabrics coated or impregnated with fluorine-containing polymers (see U.S. Pat. No. 2,539,329). Molded parts with fluorine-containing mixed polymer fabrics in thermoplastic supporting compounds that are mixed with fibers and produced by injection molding methods, have also been already proposed. Also known are molded parts with a full polymer fabric containing fluorine in a thermosetting supporting compound (see U.S. Pat. No. 2,885,248). Moreover, many methods are known by which low-friction threads are applied to the bearing side of a plain bearing by winding or weaving, with a supporting or adhering compound being subsequently sprayed or pressed around the threads.
But all hitherto-known manufacturing methods for producing a plain bearing element which is capable of withstanding great pressures and high temperatures and which needs no maintenance have the important drawback of being feasible only in heavily labor-intensive production operations, and such methods can hardly be considered for mass production operations.
On the other hand, a suggestion is already also known, according to which PTFE (polytetrafluoroethylene) threads and metal threads are to be processed into a double-sided fabric. That particular side of the double-sided fabric which shows essentially the metal threads is then intended to be soldered continuously to a base strip or supporting band. Individual plain bearing parts are then supposed to be cut or formed from the laminated band that is obtained by the above soldering of the supporting band and the mixed fabric band together. Practice has shown, however, that the solder connections in such a known laminated material are not suited to withstand, without damage, the conventional production operations that are used in forming plain bearing parts out of compound or laminate material bands, and do not provide a sufficiently reliable bond between the compound or composite fabric and the supporting body in the finished bearing part.